Sounds like you have most of it covered , the one car I built literally ran the battery dead while driving it as it had so many power options added , so you want a 12v bus or a fuse block , every GM truck has a bus under hood [it is a connector strip with 5-6 posts on it ], use relays for everything & shunt the power from the bus, so connect everything to the bus that is not stock this will keep all the power all under hood , connect the battery to the bus , as the battery drops the reg will tell the alt to charge to keep up with the draw as needed . I would add fusable link to each circuit off the bus or you can jump the battery to an under hood fuse block & skip the bus most modern cars are this way with a relay & underhood fuse block , this way any power for the accessories added will not go through the firewall or ammeter at all .
We were running 2 electric fans , an electric water pump , 2 electric fuel pumps , EFI computer , & all of the stock systems with a 60 amp alt it went dead while running LOL
